388 lines
11 KiB
Python
388 lines
11 KiB
Python
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"""Tools for constructing domains for expressions. """
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from math import prod
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from sympy.core import sympify
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from sympy.core.evalf import pure_complex
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from sympy.core.sorting import ordered
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from sympy.polys.domains import ZZ, QQ, ZZ_I, QQ_I, EX
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from sympy.polys.domains.complexfield import ComplexField
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from sympy.polys.domains.realfield import RealField
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from sympy.polys.polyoptions import build_options
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from sympy.polys.polyutils import parallel_dict_from_basic
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from sympy.utilities import public
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def _construct_simple(coeffs, opt):
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"""Handle simple domains, e.g.: ZZ, QQ, RR and algebraic domains. """
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rationals = floats = complexes = algebraics = False
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float_numbers = []
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if opt.extension is True:
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is_algebraic = lambda coeff: coeff.is_number and coeff.is_algebraic
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else:
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is_algebraic = lambda coeff: False
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for coeff in coeffs:
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if coeff.is_Rational:
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if not coeff.is_Integer:
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rationals = True
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elif coeff.is_Float:
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if algebraics:
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# there are both reals and algebraics -> EX
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return False
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else:
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floats = True
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float_numbers.append(coeff)
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else:
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is_complex = pure_complex(coeff)
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if is_complex:
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complexes = True
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x, y = is_complex
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if x.is_Rational and y.is_Rational:
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if not (x.is_Integer and y.is_Integer):
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rationals = True
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continue
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else:
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floats = True
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if x.is_Float:
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float_numbers.append(x)
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if y.is_Float:
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float_numbers.append(y)
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elif is_algebraic(coeff):
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if floats:
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# there are both algebraics and reals -> EX
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return False
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algebraics = True
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else:
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# this is a composite domain, e.g. ZZ[X], EX
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return None
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# Use the maximum precision of all coefficients for the RR or CC
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# precision
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max_prec = max(c._prec for c in float_numbers) if float_numbers else 53
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if algebraics:
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domain, result = _construct_algebraic(coeffs, opt)
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else:
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if floats and complexes:
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domain = ComplexField(prec=max_prec)
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elif floats:
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domain = RealField(prec=max_prec)
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elif rationals or opt.field:
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domain = QQ_I if complexes else QQ
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else:
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domain = ZZ_I if complexes else ZZ
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result = [domain.from_sympy(coeff) for coeff in coeffs]
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return domain, result
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def _construct_algebraic(coeffs, opt):
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"""We know that coefficients are algebraic so construct the extension. """
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from sympy.polys.numberfields import primitive_element
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exts = set()
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def build_trees(args):
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trees = []
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for a in args:
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if a.is_Rational:
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tree = ('Q', QQ.from_sympy(a))
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elif a.is_Add:
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tree = ('+', build_trees(a.args))
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elif a.is_Mul:
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tree = ('*', build_trees(a.args))
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else:
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tree = ('e', a)
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exts.add(a)
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trees.append(tree)
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return trees
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trees = build_trees(coeffs)
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exts = list(ordered(exts))
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g, span, H = primitive_element(exts, ex=True, polys=True)
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root = sum([ s*ext for s, ext in zip(span, exts) ])
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domain, g = QQ.algebraic_field((g, root)), g.rep.rep
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exts_dom = [domain.dtype.from_list(h, g, QQ) for h in H]
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exts_map = dict(zip(exts, exts_dom))
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def convert_tree(tree):
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op, args = tree
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if op == 'Q':
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return domain.dtype.from_list([args], g, QQ)
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elif op == '+':
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return sum((convert_tree(a) for a in args), domain.zero)
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elif op == '*':
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return prod(convert_tree(a) for a in args)
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elif op == 'e':
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return exts_map[args]
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else:
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raise RuntimeError
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result = [convert_tree(tree) for tree in trees]
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return domain, result
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def _construct_composite(coeffs, opt):
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"""Handle composite domains, e.g.: ZZ[X], QQ[X], ZZ(X), QQ(X). """
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numers, denoms = [], []
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for coeff in coeffs:
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numer, denom = coeff.as_numer_denom()
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numers.append(numer)
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denoms.append(denom)
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polys, gens = parallel_dict_from_basic(numers + denoms) # XXX: sorting
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if not gens:
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return None
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if opt.composite is None:
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if any(gen.is_number and gen.is_algebraic for gen in gens):
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return None # generators are number-like so lets better use EX
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all_symbols = set()
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for gen in gens:
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symbols = gen.free_symbols
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if all_symbols & symbols:
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return None # there could be algebraic relations between generators
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else:
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all_symbols |= symbols
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n = len(gens)
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k = len(polys)//2
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numers = polys[:k]
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denoms = polys[k:]
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if opt.field:
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fractions = True
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else:
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fractions, zeros = False, (0,)*n
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for denom in denoms:
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if len(denom) > 1 or zeros not in denom:
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fractions = True
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break
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coeffs = set()
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if not fractions:
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for numer, denom in zip(numers, denoms):
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denom = denom[zeros]
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for monom, coeff in numer.items():
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coeff /= denom
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coeffs.add(coeff)
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numer[monom] = coeff
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else:
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for numer, denom in zip(numers, denoms):
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coeffs.update(list(numer.values()))
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coeffs.update(list(denom.values()))
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rationals = floats = complexes = False
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float_numbers = []
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for coeff in coeffs:
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if coeff.is_Rational:
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if not coeff.is_Integer:
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rationals = True
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elif coeff.is_Float:
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floats = True
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float_numbers.append(coeff)
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else:
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is_complex = pure_complex(coeff)
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if is_complex is not None:
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complexes = True
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x, y = is_complex
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if x.is_Rational and y.is_Rational:
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if not (x.is_Integer and y.is_Integer):
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rationals = True
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else:
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floats = True
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if x.is_Float:
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float_numbers.append(x)
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if y.is_Float:
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float_numbers.append(y)
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max_prec = max(c._prec for c in float_numbers) if float_numbers else 53
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if floats and complexes:
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ground = ComplexField(prec=max_prec)
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elif floats:
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ground = RealField(prec=max_prec)
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elif complexes:
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if rationals:
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ground = QQ_I
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else:
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ground = ZZ_I
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elif rationals:
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ground = QQ
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else:
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ground = ZZ
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result = []
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if not fractions:
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domain = ground.poly_ring(*gens)
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for numer in numers:
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for monom, coeff in numer.items():
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numer[monom] = ground.from_sympy(coeff)
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result.append(domain(numer))
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else:
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domain = ground.frac_field(*gens)
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for numer, denom in zip(numers, denoms):
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for monom, coeff in numer.items():
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numer[monom] = ground.from_sympy(coeff)
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for monom, coeff in denom.items():
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denom[monom] = ground.from_sympy(coeff)
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result.append(domain((numer, denom)))
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return domain, result
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def _construct_expression(coeffs, opt):
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"""The last resort case, i.e. use the expression domain. """
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domain, result = EX, []
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for coeff in coeffs:
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result.append(domain.from_sympy(coeff))
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return domain, result
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@public
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def construct_domain(obj, **args):
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"""Construct a minimal domain for a list of expressions.
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Explanation
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===========
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Given a list of normal SymPy expressions (of type :py:class:`~.Expr`)
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``construct_domain`` will find a minimal :py:class:`~.Domain` that can
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represent those expressions. The expressions will be converted to elements
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of the domain and both the domain and the domain elements are returned.
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Parameters
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==========
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obj: list or dict
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The expressions to build a domain for.
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**args: keyword arguments
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Options that affect the choice of domain.
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Returns
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=======
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(K, elements): Domain and list of domain elements
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The domain K that can represent the expressions and the list or dict
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of domain elements representing the same expressions as elements of K.
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Examples
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========
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Given a list of :py:class:`~.Integer` ``construct_domain`` will return the
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domain :ref:`ZZ` and a list of integers as elements of :ref:`ZZ`.
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>>> from sympy import construct_domain, S
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>>> expressions = [S(2), S(3), S(4)]
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>>> K, elements = construct_domain(expressions)
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>>> K
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ZZ
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>>> elements
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[2, 3, 4]
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>>> type(elements[0]) # doctest: +SKIP
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<class 'int'>
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>>> type(expressions[0])
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<class 'sympy.core.numbers.Integer'>
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If there are any :py:class:`~.Rational` then :ref:`QQ` is returned
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instead.
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>>> construct_domain([S(1)/2, S(3)/4])
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(QQ, [1/2, 3/4])
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If there are symbols then a polynomial ring :ref:`K[x]` is returned.
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>>> from sympy import symbols
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>>> x, y = symbols('x, y')
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>>> construct_domain([2*x + 1, S(3)/4])
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(QQ[x], [2*x + 1, 3/4])
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>>> construct_domain([2*x + 1, y])
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(ZZ[x,y], [2*x + 1, y])
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If any symbols appear with negative powers then a rational function field
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:ref:`K(x)` will be returned.
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>>> construct_domain([y/x, x/(1 - y)])
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(ZZ(x,y), [y/x, -x/(y - 1)])
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Irrational algebraic numbers will result in the :ref:`EX` domain by
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default. The keyword argument ``extension=True`` leads to the construction
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of an algebraic number field :ref:`QQ(a)`.
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>>> from sympy import sqrt
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>>> construct_domain([sqrt(2)])
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(EX, [EX(sqrt(2))])
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>>> construct_domain([sqrt(2)], extension=True) # doctest: +SKIP
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(QQ<sqrt(2)>, [ANP([1, 0], [1, 0, -2], QQ)])
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See also
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========
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Domain
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Expr
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"""
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opt = build_options(args)
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if hasattr(obj, '__iter__'):
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if isinstance(obj, dict):
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if not obj:
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monoms, coeffs = [], []
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else:
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monoms, coeffs = list(zip(*list(obj.items())))
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else:
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coeffs = obj
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else:
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coeffs = [obj]
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coeffs = list(map(sympify, coeffs))
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result = _construct_simple(coeffs, opt)
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if result is not None:
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if result is not False:
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domain, coeffs = result
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else:
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domain, coeffs = _construct_expression(coeffs, opt)
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else:
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if opt.composite is False:
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result = None
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else:
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result = _construct_composite(coeffs, opt)
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if result is not None:
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domain, coeffs = result
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else:
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domain, coeffs = _construct_expression(coeffs, opt)
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if hasattr(obj, '__iter__'):
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if isinstance(obj, dict):
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return domain, dict(list(zip(monoms, coeffs)))
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else:
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return domain, coeffs
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else:
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return domain, coeffs[0]
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